In the oil and gas production industry, natural gas wells frequently also produce salt water with the gas. This salt water frequently comes from the same geologic formation as the gas, and when lifted to the surface with the produced gas, must be disposed of in a safe and ecological manner. This fact places an economic burden upon a gas well since the salt water may only be disposed of in state regulated and approved wells, which frequently require the water to be trucked great distances due to their locations. Frequently, a pump jack must be used to lift the water to the surface. These are expensive to operate and have high maintenance costs and down time. In addition to the costs of pumping the water up, storage facilities must be provided on location to safely store the water. Trucking the water is costly, and a fee must be paid to use the state approved water disposal well. Thus, the concurrent production of salt water with natural gas places a heavy economic burden upon the gas well. Many otherwise profitable wells are rendered unprofitable by the economic burden of produced salt water.
In gas wells that produce salt water, there has to date been no choice but to produce the water with the gas. If the water is not removed from the well bore, a column of water will rise vertically up the well bore until the hydraulic head of this column has become equal to the pressure of the formation from which it originated. When this point of equilibrium is reached, no further gas production will occur and the well will remain in this state until the hydrostatic head is decreased.
The use of plunger pumps to produce oil from a well having usable gas pressure is well known. In basic principle, a plunger pump is dropped from the surface through the well casing or tubing and into the oil/gas mixture downhole. A mechanism, typically one operated by hydrostatic pressure, closes a passage in the plunger pump to allow gas pressure to build up beneath the pump. The gas pressure builds to a point where it lifts the pump, and a quantity of oil above the pump, to the surface where the oil is recovered. The gas pressure beneath the pump is relieved to allow the pump to fall downhole again to re-initiate the sequence.
One example of a plunger pump is disclosed in U.S. Pat. No. 4,070,134, issued Jan. 24, 1978 to Gramling. However, this device has not proven reliable in actual use, and a need exists for an improved plunger pump which provides for efficient production of oil, condensate, and de-watering of gas wells, either through casing or tubing. For simplicity, the following discussion will be limited to the plunger pump application in casing, with the understanding that the same principles of operation can be applied to its use in tubing.